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-Kernel driver pc87427
-Supported chips:
- * National Semiconductor PC87427
- Prefix: 'pc87427'
- Addresses scanned: none, address read from Super I/O config space
- Datasheet: No longer available
-Author: Jean Delvare <>
-Thanks to Amir Habibi at Candelis for setting up a test system, and to
-Michael Kress for testing several iterations of this driver.
-The National Semiconductor Super I/O chip includes complete hardware
-monitoring capabilities. It can monitor up to 18 voltages, 8 fans and
-6 temperature sensors. Only the fans and temperatures are supported at
-the moment, voltages aren't.
-This chip also has fan controlling features (up to 4 PWM outputs),
-which are partly supported by this driver.
-The driver assumes that no more than one chip is present, which seems
-Fan Monitoring
-Fan rotation speeds are reported as 14-bit values from a gated clock
-signal. Speeds down to 83 RPM can be measured.
-An alarm is triggered if the rotation speed drops below a programmable
-limit. Another alarm is triggered if the speed is too low to be measured
-(including stalled or missing fan).
-Fan Speed Control
-Fan speed can be controlled by PWM outputs. There are 4 possible modes:
-always off, always on, manual and automatic. The latter isn't supported
-by the driver: you can only return to that mode if it was the original
-setting, and the configuration interface is missing.
-Temperature Monitoring
-The PC87427 relies on external sensors (following the SensorPath
-standard), so the resolution and range depend on the type of sensor
-connected. The integer part can be 8-bit or 9-bit, and can be signed or
-not. I couldn't find a way to figure out the external sensor data
-temperature format, so user-space adjustment (typically by a factor 2)
-may be required.